Over the past few months, pilots have conducted several test flights of the space-launch vehicle Eve. The mother ship—named after the billionaire's mum—is designed to ferry SpaceShipTwo and its two pilots and six astronauts more than 50,000 feet above the Earth's surface.

From the stratosphere, SpaceShipTwo would blast to a suborbital altitude of about 360,000 feet using hybrid rockets.

A "whole new era of space travel" may be nigh, boasted Branson, who plans to go boldly where just a few tourists have gone before. SpaceShipTwo is slated for completion by the end of the year, he said, followed by about 18 months of testing.

Scientists James Lovelock and Stephen Hawking are among 300 passengers queued up to ride in Branson's spacecraft. Contrary to rumors, "Star Trek" alumnus William Shatner is not among them, Virgin Galactic President Will Whitehorn said in an interview.

A ticket to ride is $200,000—perhaps chump change for Branson but a king's ransom for the rest of us. It is the "trip of a lifetime," Virgin Galactic's online portal promises.

"Reserve your place in space now and look forward to three days of training in preparation with your crew," the sales pitch continues. "Traveling at over three times the speed of sound to a distance of around 360,000 feet above the Earth's surface, experience weightlessness and enjoy the breathtaking view."

Shortly before SpaceShipTwo reaches the apogee of its flight path, the vessel would fold its wings for re-entry through the upper atmosphere. The ship's wings would flatten out once more at 60,000 feet in order to glide back to terra firma.

Eye on emissions, fuel savings

Virgin Galactic uses a landing strip in California's Mojave Desert now, but construction crews plan to break ground next month on a state-of-the-art "spaceport" near Truth or Consequences, N.M.

The project's terminal and hangar facility, designed by URS Corp. and Foster + Partners, will feature solar-thermal panels. A passive cooling system will draw in hot air from the outside and chill it through a series of concrete tubes.

Virgin Galactic's spacecraft were also designed with environmental sustainability in mind, Whitehorn said.

Mother ship Eve's jet engines will run on kerosene initially but are also capable of running on butanol, a biofuel that can be made from algae. SpaceShipTwo's rockets will burn nitrous oxide —but only briefly—as the spaceship would require no fuel for takeoff, reentry and landing.

According to Whitehorn's calculations,

carbon dioxide emissions per passenger on a Virgin Galactic spaceflight would be about 60 percent of a passenger's carbon footprint on a round-trip flight between New York and London. About 70 percent of a spaceflight's CO2 emissions would come from mother ship Eve, which must carry SpaceShipTwo into the stratosphere.

To lighten the load, both spacecraft are made of carbon-composite materials. Swiss adventurer Andre Piccard, a hot-air balloon enthusiast like Branson, is building an experimental aircraft of his own with such lightweight materials.

Piccard aims to take his 1,500-kilogram "Solar Impulse" aircraft around the world using only the power of the sun (Greenwire, October 31, 2008).

"The basic idea of lightweighting spacecraft or aircraft is going to use a lot less fuel," said Frances Arnold, a professor of biochemistry and chemical engineering at the California Institute of Technology. "The same is true of any kind of vehicle."

Virgin Galactic's use of a mother ship, as opposed to a ground-based launch, will also save fuel, said Rob Anderson, a budding Cambridge University scientist. He is one of seven students planning a high-altitude rocket launch later this year.

The "Cambridge University Spaceflight" team's mission is to deliver payload to space as cheaply and efficiently as possible—or for about $32,000, in this case. The team plans to send a helium balloon up 18.6 miles, at which point a rocket would blast solo to an elevation of 62.1 miles.

Anderson said a balloon-based model would work best for small scientific payloads; the latex balloon will eventually pop as its helium expands. But he predicted that the day when lightweight spaceships carry tourists is not too far away.

"At the speed things are going today, I suspect we'll see a lot of it," Anderson added.

'Exciting days'

A half-dozen space tourists have flown to and from the International Space Station aboard Russian Soyuz rockets since 2001. Two years ago, Google, Inc., and the X Prize Foundation offered $20 million to the first privately funded team that could launch a robot into space, travel at least 500 meters over the moon's surface and send images and data back to Earth by the end of 2012.

Eighteen teams from around the world are vying for the "Google Lunar X Prize," according to the organization's Web site.

Virgin Galactic hopes to fly 500 people to space in its first year of commercial flights and 50,000 over a decade. The Federal Aviation Administration has yet to issue a commercial license to the company, Whitehorn said, so its spaceships must fly in the name of environmental science for now.

When test flights begin next year, Eve and SpaceShipTwo will be equipped with National Oceanic & Atmospheric Administration instruments to measure carbon dioxide, methane and other heat-trapping gases in the upper atmosphere. NOAA's weather balloons are limited to conducting research at about 25,000 feet up, Whitehorn noted.

"Hopefully, we will develop a commercial relationship with them in the future once we get the license," he added.

As for Virgin Galactic's eventual tourists, will they develop a greener relationship with the blue planet they call home?

"If the people who have the money to go up there then decide to devote their resources to saving that little blue gem they see, then that would be a good outcome," offered Caltech's Arnold.

A recent blog post by Britain's Guardian newspaper is less sanguine.

"Why doesn't Virgin Galactic just call it as it is?" the blog petitioned. "Sure, sell your dreams of space flight to the super-rich if you must...but let's not keep up the pretence that it isn't one of the most extravagant and self-centered uses of fossil fuel imaginable."

For what it's worth, Branson is investing $3 billion worth of profits from his "dirty" transportation businesses in clean-energy technologies. He is also looking beyond the Earth's orbit.

"Exciting days," he said. "Now, whether we'll ever go to the moon? ... I think we'll give the moon a miss and go straight to Mars."